My DYLD_LIBRARY_PATH is set correctly (it's finding libcudart.dybli above). I have a mac book pro with an NVIDIA GeForce 320M 256 MB running OS X 10.7.1. Is there something in addition that I need to install?

We'll start shipping that in R14 to avoid this. To fix for now, please install the CUDA 4.0 toolkit. You might also need to set DYLD_LIBRARY_PATH to have both /usr/local/cuda/lib and /usr/local/cula/lib.